1. Field of the Invention
The present invention relates to a multi-cylinder engine.
2. Background Art
Conventionally, there is well known a multi-cylinder engine that each of the cylinders has a fuel injection valve. With regard to such an engine, when fuel injection failure, such as insufficient combustion, misfire or trouble of a fuel injection valve, occurs in one of cylinders, stable driving state cannot be obtained. Then, there is also well known an engine which has function of detecting a fuel injection failure cylinder.
The Japanese Patent Laid Open Gazette 2001-241353 discloses a control art as an abnormal cylinder detection means of a multi-cylinder internal combustion engine that a misfire or excessive combustion cylinder is judged based on comparison of rotation speed difference between momentary maximum rotation speed and momentary minimum rotation speed of each cylinder at an explosion process and average rotation speed change difference of all the cylinders. The Japanese Patent Laid Open Gazette 2004-308464 discloses a control art that the fuel injection valve causing the abnormality is specified based on only rotation speed change difference between the cylinders following fuel injection of an internal combustion engine having a plurality of fuel injection valves.
With regard to the art disclosed in the Japanese Patent Laid Open Gazette 2001-241353, according to the purpose of the engine or combination congeniality with a fuel injection device, the momentary rotation speed of the cylinder causing the fuel injection abnormality may not be the minimum, whereby the misfire of or excessive combustion cylinder may not be judged. With regard to the art disclosed in the Japanese Patent Laid Open Gazette 2004-308464, the judgment is executed based on the relative information between the cylinders. Then, when all the cylinders are deteriorated with time, the fuel injection abnormality may not be detected.